needed x86-64 while all detected is i1586

i tryed to install fedora 9 on a computer i through together out of spare parts lying around the shop. the computer works fin and i have windows xp running on it. so i tryed to install fedora 9 and i got a message that said i needed a x86-64 when all it can detect is a i1586. could anyone tell me ether what this means or how to fix it or will i need to download a different version for this computer.